1. Field of the Invention
A present invention relates to a module, and in particular to a latch structure in a module such as a pluggable optical module whose outer structure is prescribed according to MSA (Multi Source Agreement).
2. Description of the Related Art
A pluggable optical module is generally known as an optical module which can be easily inserted/withdrawn (or mounted/demounted, mated/demated, engaged/disengaged) into/from rails, connectors, etc. on a mounting device for the module, one example of which is shown in FIGS. 7 and 8.
FIG. 7 shows, an exterior squint view of such a module, which is schematically composed of a tab (or pinch, lug) 1 and a case (housing) 2 and a lid 11. The lid 11 is a roof covering the case 2 and is provided with a radiator 11a. To this case 2, a nail 4 is accessible for engaging a latch between the module and a mounting device (not shown), namely the nail 4 goes in or goes out of the case 2. Between the case 2 and the lid 11, a print circuit board (not shown) is accommodated. The tab 1 and the case 2 are separated by a flange 5, and the tab 1 is provided with a connector plug portion 12 for plugging a transmitting/receiving connector for an optical cable.
FIG. 8 shows an exploded squint view of the module shown in FIG. 7. The tab 1 is fitted over a connector portion 2e in the case 2 comprising connector plug portions 12a, 12b forming the connector plug portion 12. In the connector plug portions 12a, 12b, hooks 15a, 15b are respectively fitted and engaged with optical devices 14a, 14b. 
While this pluggable optical module comprises a latching/unlatching structure with a mounting device which enables an insertion/withdrawal into/from rails, connectors, etc. thereon, it is necessary to provide the latching/unlatching structure in a limited area on both sides in the presence of optical parts and electronic parts, as shown in FIG. 8.
The case 2 is provided with ditches (grooves) 2a1, 2a2 near both sides into which metallic fittings 16a, 16b are inserted and held. These metal fittings 16a, 16b are respectively engaged with latching nails (pawls) 41, 42. These nails 41, 42 are respectively provided with pins 4a1, 4a2 and springs 4b1, 4b2, so that springs 33 are engaged with the metal fittings 16a, 16b as accommodated in the ditches 2a1, 2b2 and springs 4b1, 4b2 are respectively engaged with the nails 41, 42, whereby nails 41, 42 go in and go out of openings 2b1, 2b2 provided in the ditches 2a1, 2a2. Namely, by pulling the tab 1 in the direction apart from the case 2, the nails 41, 42 are recessed or withdrawn from the openings 2b1, 2b2, whereby the latch with a fitting portion (not shown) for the rails, etc. on the mounting device is disengaged. To the contrary, by releasing the tab 1, tips of the nails 41, 42 project from the openings 2b1, 2b2 and engage in fitting holes of the rails, etc. on the mounting device to be latched so that the module may not detached.
Also in the case 2, a print circuit board (PCB) 13 mounting thereon an LSI 13a is accommodated. By covering the case 2 having accommodated the print circuit board 13 with the lid 11 and screwing screws 11b–11f, such a module as shown in FIG. 7 is assembled.
In FIG. 9, a latching structure among the tab 1, the case 2, the nail 4, and the metal fitting 16 shown in FIG. 8 is intelligibly shown in an enlarged view. It is to be noted that while this latching structure is provided on both sides of the case 2 as shown in FIG. 8, for the simplification of figure, only one side is shown so that in FIG. 9, the ditches 2a1, 2a2 are represented by reference numeral “2a”, the openings 2b1, 2b2 by a reference numeral “2b”, the metal fittings 16a, 16b by a reference numeral “16”, the pins 4a1, 4a2 by a reference numeral “4”, and the springs 4b1, 4b2 by a reference numeral “4b”, respectively in the same manner. This applies to the following descriptions.
Firstly, the nail 4 is inserted into or fitted in the ditch 2a. At this time, the spring 4b is inserted into a blind hole 4c, so that a tip 4d of the nail 4 may go out of the opening 2b by the elastic force of the spring 4b. Under this condition, the metal fitting 16 is also inserted into the ditch 2a so that the pin 4a of the nail 4 may be inserted into a triangular hole 16c provided in the metal fitting 16. At this time, the spring 4b is to be positioned on the right side of a spring support 16b2. Concurrently, a head of the metal fitting 16, which is on the opposite side to the triangle hole 16c, is pulled out of the opening 2d of the ditch 2a, and the spring 33 is engaged with a spring support 16b2. The metallic fitting 16 is further provided with a screw hole 16d to which the screw 1b is fixedly screwed from a screw hole 1a of the tab 1. It is to be noted that the spring support 16b1 is provided so that it may be diverted even on the opposite side of the case 2, which achieves no particular effect in the arrangement of FIG. 9.
After the module having a latch structure thus assembled is latched into the mounting device, the tab 1 is pulled in X direction shown against the elastic force of the spring 33 whereby the metal fitting 16 is concurrently pulled and the pin 4a of the nail 4 moves along a diagonal plane from a position shown by dotted lines within the triangle hole 16c so that a tip 4d of the nail 4 is recessed from the opening 2b against the elastic force of the spring 4d in Y direction perpendicular to X direction, whereby the nail 4 becomes off the rail or the like on the mounting device, disengaging the latch between the case 2 and the mounting device. Namely, the metallic fitting 16 is to convert the pulling force in X direction into a force in Y direction, i.e. to make an XY directional conversion.
In a state where the tab 1 is not pulled, or the tab 1 is released, the metal fitting 16 is returned in the reverse direction to X direction through the spring support 16b2 by the elastic force of the spring 33, so that the pin 4a returns to the position shown by dotted lines in the triangle hole 16c of the metal fitting 16 whereby the tip 4d of the nail 4 projects from the opening 2b to automatically latch into the mounting device. On an occasion where the module is fitted in the rails or the like on the mounting device, an inclined plane provided in the tip 4d of the nail 4 contacts with the rail or the like to automatically withdraw the nail and projects again at the fitting hole to be latched.
Thus, in the state where the tab 1 is not pulled in X direction, the nail 4 projecting out of the side of the case 2 of the module is engaged with the rail or the like on the mounting device, so that the module is not disengaged even in the occurrence of vibrations or the like.
Thus, with the tab 1 being pulled in X direction or released, the nail 4 moves in Y direction perpendicular to X direction, thereby going in and going out of the opening 2b, and engaging or disengaging the latch with the mounting device.
On the other hand, to release a lock by pulling, there is conventionally proposed a connector in which a front and rear pair of sliders are fitted to a male housing and is for movement back and forth by a coil spring; a female housing is provided with a tension arm in addition to a lock arm which can press the front slides at insertion-coupling; detachment of the both housings is carried out by pulling the female housing backward after lock with a lock arm is released; a hook part of the tension arm is locked to a hooked part and the rear slider is pulled forward compressing the coil spring; if pulled to a given extent, lock is released and the female housing is pulled off; when a pulling-off operation is suspended halfway, the rear slider is put back to the rear halting position by resilient force of the coil spring, and the female housing is put back to the proper insertion-coupling position through the tension arm (see e.g. patent document 1).
Also there is proposed an electronic assembling apparatus having guiding planes formed in a connector base orthogonally to the direction of the plugging contacts of the connector base, and having guiding means parallel with a rear wall and provided oppositely to the guiding planes without any idle members in the inside of a assembling housing portion; further, in this electronic assembling apparatus, the dimension of the diameter of each through hole provided in a printed board which serves for fastening the printed wiring board to the inside of the assembling housing portion by each screw is set larger than the diameter of the axial portion of each used screw by a nearly equivalent quantity to the sum of the manufacturing errors of constituents portions intended to be assembled (see e.g. patent document 2).    [Patent document 1] Japanese patent application laid-open No. 2002-184526    [Patent document 2] Japanese patent application laid-open No. 2003-347771
However, the prior art as shown in FIG. 9 in such a module having a latching/unlatching structure in a limited area in the existence of optical parts and electronic part has the following disadvantages;
(1) Since the tab is fixed with the metallic fitting by screws, even a little displacement of the pulling direction of the tab from X direction will effect on the force component toward Y direction, which makes the stroke or displacement of the nail insufficient, disabling the latch with the mounting device to be disengaged.
Also, the position of the tab held may be displaced from the position where a metallic fitting applies the force to the pin of the nail. Frequently repeated operations of the tab will loose the screws to decline the tab and make members rub each other and difficult to be moved, which will also reduce the displacement of the nail in Y direction. Furthermore, mutual rubs between members will shorten the life due to wear.
(2) On the other hand, it is conceivable in the prior art shown in FIG. 9 that the above problem (1) is solved by supposing that the screw hole 16d provided in the metal fitting 16 is formed as for example a blind hole, which is engaged with the projecting portion of the screw 1b projecting inside the tab 1 through the screw hole 1a, and the metal fitting 16 is pulled together with the tab 1.
However, this concept would require a fixed width for performing the XY directional conversion in the triangle hole 16c of the metal fitting 16, so that the metal fittings 16 also requires the same width. Also, due to restrictions for the length of the screw 1b projecting from the tab 1, the projecting portion of the screw 1b lacks the pulling force for the metallic fitting 16 through the blind hole 16a, in which the pulling force in X direction is not sufficiently transferred to that in Y direction, thereby lacking the stroke of the metallic fitting 16 for displacing the nail in Y direction. Accordingly, in view of the size of rails provided on the mounting device being prescribed according to MSA, the above concept would not meet the requirement that the latching stroke of the nail 4 be larger than a fixed value.
(3) Because of the metallic fitting being fixed inside the tab, the mounting angle of the metal fitting is effected by the precision of engaged face of the tab with respect to the case. Therefore, the opening angle of the tab will be varied to worsen the movement of the nail due to the contact with the inside face of the ditch of the case, resulting in a difficulty in assembly.
(4) There are a large number of parts such as springs for moving the nail, springs for returning the tab, and a metal fitting for transferring forces, which becomes a factor of cost increases.